JP6799282B2 - Silver reflector and its manufacturing method and inspection method - Google Patents

Description

The present invention relates to a silver reflector that is durable when used in a hot and humid environment and can suppress deformation of the optical surface due to film stress, and a method for manufacturing and an inspection method thereof.

As a reflecting mirror, there is one in which a reflective film containing silver is formed on a base material (for example, Patent Documents 1 to 3). In such a reflecting mirror, it is an issue to suppress a change in the shape of an optical surface, improve the adhesion of the reflecting film, and improve the corrosion resistance of the reflecting film. In particular, reflectors that are placed in harsh usage environments such as in-vehicle products are required to have extremely high environmental resistance.

In Patent Document 1, a light reflecting mirror in which a reflective film containing silver is formed on the surface of a plastic base material, the plastic base material is a thermosetting resin molded product, and the adhesion improving film is Cr, Al. It is described that the reflection increasing layer is composed of _two layers such as Y ₂ O ₃ , Al ₂ O _{3 and} others, and is formed of ₂ O ₃ , LaTiO ₃ and others. Here, each film constituting the reflective film is formed by thin-film deposition using plasma.

Patent Document 2 describes a reflecting mirror having a structure in which a film mainly composed of aluminum oxide is directly formed on both sides of a silver film, and both aluminum oxide-based films on both sides are aluminum oxide or aluminum nitride. Those consisting of are described. Here, the aluminum oxide-based film is formed by a sputtering method, an ion beam assisted vapor deposition method, or the like.

Patent Document 3 describes a laser having a base material layer, a stress adjusting film formed on the base material layer and deforming the base material layer into a convex shape, and a reflection film formed on the stress adjusting film. An optical optical mirror having a stress adjusting film containing either zinc sulfide, cerium oxide, or silicon oxide is described. Here, the stress adjusting film is formed by physical assist including ions or plasma.

The above-mentioned Patent Document 1 mentions the resistance of the reflective film to the environment, but a specific method or quantitative explanation is given as to what kind of configuration can achieve how much high durability. Absent.

Regarding Patent Document 2, the reflectance is improved by heat treatment at 50 ° C. to 200 ° C., but for conditions including moisture resistance, only the change in reflectance is measured at a temperature of 70 ° C. and a humidity of 90%. Yes, there is no disclosure of specific methods for improving moisture resistance.

Patent Document 3 has a structure in which deformation of a convex surface is suppressed by a stress adjusting film having a tensile stress that cancels the tensile stress of the Ag film, but disclosure of durability in a high temperature environment or a high temperature and high humidity environment. There is no.

Japanese Unexamined Patent Publication No. 2006-133331 International release WO2005 / 029142 JP-A-2009-116263

The present invention has been made in view of the above background technology, and can maintain the high reflection characteristics achieved by using silver even in a high temperature and high humidity environment, and suppress the film stress to a small value to suppress the surface deformation of the optical surface. It is intended to provide a silver reflector that can.

Another object of the present invention is to provide a method for manufacturing a silver reflector having high durability and performance and a method for inspecting the silver reflector.

In order to achieve the above object, in the silver reflector according to the present invention, the underlying adhesive layer, the main silver layer formed on the adhesive layer, and the hyperreflecting layer formed on the main silver layer are used as a reflective film. In the silver reflecting mirror provided, the main silver layer is formed of either silver or an alloy mainly composed of silver, and the film stress after the film formation of the reflective film is in the range of +100 MPa to -100 MPa and reflects. The film stress after the film is put into a high temperature drying environment of 110 ° C. for 24 hours is in the range of +100 MPa to -100 MPa, and the reflective film after being put into a high temperature drying environment of 110 ° C. is hot and humid at 85 ° C. and 85% RH. The film stress after being put into the environment for 24 hours is in the range of +100 MPa to -100 MPa, and the film stress value after being put into a high temperature drying environment at 110 ° C for 24 hours and the high temperature and high humidity environment at 85 ° C and 85% RH. The absolute value of the amount of change from the film stress value after being charged for 24 hours is 40 MPa or less. Here, drying in a high-temperature drying environment means 20% RH or less.

According to the silver reflector, not only the film stress after film formation is in the range of +100 MPa to -100 MPa, but also the film stress after the reflective film is put into a high temperature drying environment at 110 ° C. for 24 hours, and 110 Since the film stress after the reflective film after being put into a high temperature and dry environment at ° C. is put into a high temperature and high humidity environment at 85 ° C. and 85% RH for 24 hours is in the range of +100 MPa to -100 MPa, it is applied to the substrate or the like. Stress can be reduced to reduce surface deformation of the optical surface. Further, the absolute value of the amount of change between the film stress value after being put into a high temperature and dry environment of 110 ° C. for 24 hours and the film stress value after being put into a high temperature and high humidity environment of 85 ° C. and 85% RH for 24 hours is 40 MPa or less. Therefore, it is considered that fluctuations in the film state due to the inflow and outflow of moisture due to changes in the fluctuating environment are suppressed, and shear stress is less likely to occur at the interface between the reflective film and the substrate, preventing deterioration such as peeling of the reflective film. Therefore, high reflection characteristics can be maintained even in a hot and humid environment. Specifically, for example, even after undergoing a durability test of holding in an environment of 85 ° C. and 85% RH for 1000 hours, no substantial decrease in reflectance is observed, and appearance defects such as cracks and film floating hardly occur. ..

In order to achieve the above object, the method for inspecting a silver reflector according to the present invention includes a base adhesion layer, a main silver layer formed on the adhesion layer, and a hyperreflecting layer formed on the main silver layer. This is an inspection method for a silver reflector provided as a reflective film. The main silver layer is formed of either silver or an alloy mainly composed of silver, and the film stress after the film formation of the reflective film is from +100 MPa to -100 MPa. The film stress value after the reflective film was put into a high temperature drying environment at 110 ° C. for 24 hours, and the reflective film after the reflective film was put into a high temperature drying environment at 110 ° C. for 24 hours. Is determined whether or not the absolute value of the amount of change from the film stress value after being put into a high temperature and high humidity environment of 85 ° C. and 85% RH for 24 hours is 40 MPa or less.

According to the above inspection method, it is determined whether or not the film stress after film formation is in the range of +100 MPa to -100 MPa, and the stress applied to the base material or the like is reduced to cause surface deformation of the optical surface. It is possible to confirm whether or not it is a silver reflector that can keep the amount small. Further, the absolute value of the amount of change between the film stress value after being put into a high temperature and dry environment of 110 ° C. for 24 hours and the film stress value after being put into a high temperature and high humidity environment of 85 ° C. and 85% RH for 24 hours is 40 MPa or less. Is it a silver reflector that can maintain high reflection characteristics even in a hot and humid environment by preventing deterioration such as peeling of the reflective film due to the inflow and outflow of moisture due to changes in the fluctuating environment? You can check if it is not.

In order to achieve the above object, the method for manufacturing a silver reflector according to the present invention includes a base adhesion layer, a main silver layer formed on the adhesion layer, and a hyperreflecting layer formed on the main silver layer. A method for manufacturing a silver reflector provided as a reflective film. The main silver layer is formed of either silver or an alloy mainly composed of silver, and the film stress after the film formation of the reflective film is increased from +100 MPa to -100 MPa. The film stress value after the reflective film was put into a high temperature dry environment of 110 ° C. for 24 hours, and the reflective film was put into a high temperature dry environment of 110 ° C. for 24 hours and then the reflective film was 85 ° C. 85% RH. The absolute value of the amount of change between the film stress value and the film stress value after being put into the high temperature and high humidity environment for 24 hours is 40 MPa or less.

According to the above manufacturing method, the film stress after film formation is in the range of +100 MPa to -100 MPa, and the stress applied to the substrate or the like can be reduced to reduce the surface deformation of the optical surface. Further, the absolute value of the amount of change between the film stress value after being put into a high temperature and dry environment of 110 ° C. for 24 hours and the film stress value after being put into a high temperature and high humidity environment of 85 ° C. and 85% RH for 24 hours is 40 MPa or less. Therefore, it is considered that fluctuations in the film state due to the inflow and outflow of moisture due to changes in the fluctuating environment are suppressed, and shear stress is less likely to occur at the interface between the reflective film and the substrate, preventing deterioration such as peeling of the reflective film. Therefore, high reflection characteristics can be maintained even in a hot and humid environment.

It is an enlarged cross-sectional view explaining an example of the structure of the silver reflector of an embodiment. FIG. 5 is a conceptual cross-sectional view illustrating an example of a film forming apparatus used for manufacturing the silver reflector shown in FIG. 1. It is a conceptual sectional view explaining the environmental test apparatus used for inspection or evaluation of the silver reflector of FIG. It is a conceptual cross-sectional view explaining the film stress measuring apparatus used for the evaluation of the silver reflector of FIG.

[Embodiment]
A silver reflector according to an embodiment of the present invention, a method for manufacturing the same, and the like will be described with reference to the drawings.

As shown in FIG. 1, the silver reflector 10 of the present embodiment includes a flat plate-shaped substrate 20 and a reflective film 30 which is a thin film formed on the substrate 20.

The substrate 20 is, for example, a plate-shaped member and has a flat or curved optical surface 21 covered with a reflective film 30. The substrate 20 does not have to have light transmission. The substrate 20 is made of a resin material such as polycarbonate (PC), cycloolefin polymer (COP), acrylic resin (PMMA), polyethylene terephthalate (PET), but is not limited to the resin material, but quartz, glass, and ceramics. It may be formed of other inorganic materials.

The reflective film 30 includes an adhesion layer 31 formed as a base on the optical surface 21 of the substrate 20, a main silver layer 32 formed on the adhesion layer 31, and a hyperreflection layer 33 formed on the main silver layer 32. And. That is, the main silver layer 32 is sandwiched between the adhesion layer 31 and the reflective layer 33.

It is desirable that the adhesion layer 31 is composed of two or more layers. By forming the adhesion layer 31 to two or more layers, the effect of blocking water from the substrate 20 can be enhanced. Here, the two or more layers mean a layer of a material having good adhesion to the upper main silver layer 32 and a layer of a material having good adhesion to the lower substrate 20. When the adhesion layer 31 has a one-layer structure, it is necessary to select a material having good adhesion to both the main silver layer 32 and the substrate 20, but in this case, it becomes difficult to control the film quality and stress. Further, in order to enhance the environmental resistance of the main silver layer 32, the influence of water from the substrate 20 must be taken into consideration. It is necessary to adjust the film stress of each film so that the film is in a balanced state in order to suppress the film floating, cracks, etc. caused by the stress on each film caused by the high temperature and high humidity environment and the high temperature and dry environment. .. In the above, when the adhesion between the two layers of materials selected from the viewpoint of adhesion is poor, or when it is desired to enhance the moisture blocking effect, three layers or more may be used. In the adhesion layer 31, there are several media that block water, but one is found to be preferably a layer mainly composed of aluminum oxide. As the layer mainly composed of aluminum oxide, in addition to pure aluminum oxide, "Substance M2" or "Substance M3" manufactured by Merck & Co., which contains about 5 to 10% of La ₂ O ₃ mixed with aluminum oxide, is used. Including cases. When the layer mainly made of aluminum oxide used in the adhesion layer 31 is formed without ion assist, the moisture blocking effect is recognized, but the tensile stress of the material itself is strong, and the durability in a high temperature and high humidity environment is improved. It turned out to be relatively unsuitable for holding. Therefore, the inventor of the present application has decided to use ion assist to densify the film and aim to achieve both the effect of blocking water and the effect of stress adjustment. As a result of various experiments, it was found that the resistance to high temperature and high humidity can be improved by adjusting the film formation conditions such as the output of ion assist and the film formation rate while taking into consideration the mutual relationship with the film stress of the entire layer. .. That is, it was found that a layer mainly composed of aluminum oxide formed by the ion assist method is preferable as the layer constituting the lower side of the adhesion layer 31. Further, it was found that it is preferable to use LaTIO _3, CeO ₂ , Y ₂ O _{3, and} SnO ₂ as a material having good adhesion to silver for the layer constituting the upper side of the adhesion layer 31. By using these materials, adhesion is promoted and stress adjustment becomes easy.

The adhesion layer 31 includes at least one layer mainly composed of aluminum oxide, and the layer mainly composed of aluminum oxide is formed by using an ion assist method. The film stress of the layer mainly composed of aluminum oxide is a compressive stress. As a result, it is possible to allow the passage of a small amount of water in the aluminum oxide layer to enhance the resistance to a high temperature and high humidity environment, and it is possible to secure a certain degree of compactness and strength by applying a compressive stress.

The specific adhesion layer 31 includes a first layer 31a on the substrate 20 side and a second layer 31b on the main silver layer 32 side. Both layers 31a and 31b have a thickness of about 10 nm to 200 nm, more preferably 20 nm to 100 nm. Here, the first layer 31a is a thin film layer that has a role of a buffer layer that directly adheres to the substrate 20 and also has a function of a buffer layer that allows moisture to permeate while blocking water, and the second layer 31b is directly attached to the main silver layer 32. It is a thin film layer that has a role of adhering and reliably blocking water. The first layer 31a on the substrate 20 side is a layer mainly composed of aluminum oxide as described above, and is formed by using an ion assist method. The second layer 31b for direct contact with the main silver layer 32 is a layer formed from a material selected from at least one of the _{LaTiO 3, CeO 2, Y 2} O 3 and SnO ₂ as described above, ion-assisted method Is formed using.

Regarding both layers 31a and 31b, even if the film thickness is 20 nm or less as a whole, there is an effect of improving the adhesion, but when the film thickness is 20 nm or less, the thin film is in the process of growth, and sufficient water content consisting of film continuity. The film thickness is preferably 20 nm or more in order to exert the blocking effect. On the other hand, when the film thickness is 100 nm or more, the adhesion and moisture blocking effects are sufficient, but on the other hand, there are side effects such as increasing the surface roughness of the substrate 20 and increasing the influence of film stress as the thickness increases. From the viewpoint of the adhesion layer, it is preferable that the film thickness is controlled to 100 nm or less.

The adhesion layer 31 includes at least one adjustment layer for film stress, and when two or more layers are included, one adjustment layer (details will be described later, but corresponds to one of the first and second layers 31a and 31b). In the single layer state, the film stress after being put into a high temperature and high humidity environment of 85 ° C. 85% RH for 24 hours is more compressive than the film stress after being put into a high temperature and dry environment of 110 ° C. for 24 hours. It changes in the negative direction. In this case, one of the adjusting layers is realized by applying a material having a relatively low density in which the film stress changes in the negative direction (for example, the ion assist method and balancing various conditions related to film formation and ion supply at that time). (Aluminum oxide) can ensure a state that allows some drainage and enhance resistance to a hot and humid environment. Further, the other adjusting layer (corresponding to the other of the first and second layers 31a and 31b) is 85 ° C. with respect to the film stress after being put into a high temperature drying environment of 110 ° C. for 24 hours in a single layer state. The film stress after being put into a hot and humid environment of 85% RH for 24 hours changes in the positive direction. In this case, it is judged that the other adjusting layer has a high density, can reliably block water, and the strength of the adjusting layer itself is increased. However, it is desirable to combine the other adjusting layer with a layer in which the film stress changes in the negative direction in order to prevent the film stress from increasing due to excessive density.

The functions of the pair of layers 31a and 31b constituting the close contact layer 31 will be described in more detail. First, the first layer 31a is made of a material having a lower density than the second layer 31b, so that moisture is blocked and somewhat permeated. That is, the first layer 31a secures a state in which water drains better than the second layer 31b, has a function of preventing peeling as a cushioning material for moisture, and is a reflective film 30 for a hot and humid environment. Can increase resistance to. Further, the first layer 31a is an adjusting layer for balancing the film stress, and has a relatively weak negative film stress. Here, the negative film stress means a state in which a compressive stress is applied, and is intended to stretch in the extending direction of the film, and corresponds to a state in which the density is relatively high with respect to the base material. Further, as the first layer 31a, in the state of a single layer, with respect to the film stress after being put into a high temperature drying environment at an ambient temperature of 110 ° C. and a relative humidity of 20% RH or less (specifically, the humidity is substantially zero) for 24 hours. Select a film in which the film stress changes in the negative direction after being put into a high temperature and high humidity environment having an ambient temperature of 85 ° C. and a relative humidity of 85% RH for 24 hours. The compressive stress of the first layer 31a is increased by the above-mentioned humidity-increasing environmental test, and it is determined that appropriate water drainage or moisture permeation is ensured. It is desirable that the first layer 31a is combined with the second layer 31b in which the film stress changes in the positive direction from the viewpoint of adjusting the film stress and other viewpoints.

On the other hand, the second layer 31b is formed of a material having a higher density than the first layer 31a, thereby ensuring a state in which water drainage is not as good as that of the second layer 31b, and the main silver layer. 32 can be protected to increase the resistance of the reflective film 30 to a hot and humid environment. Further, the second layer 31b is an adjusting layer for balancing the film stress, and has a negative film stress of a certain level or more. Further, as the second layer 31b, in the state of a single layer, with respect to the film stress after being put into a high temperature drying environment at an ambient temperature of 110 ° C. and a relative humidity of 20% RH or less (specifically, the humidity is substantially zero) for 24 hours. Select a film that changes the film stress in the positive direction after being put into a high-temperature and high-humidity environment with an ambient temperature of 85 ° C. and a relative humidity of 85% RH for 24 hours. The second layer 31b has a slightly reduced compressive stress by the above-mentioned humidity-increasing environmental test, and is judged to have a high moisture blocking effect.

In the present embodiment, the main silver layer 32 is a thin film formed only of silver. The main silver layer 32 has a thickness of about several tens of nm to 100 nm, more preferably about 50 nm to 100 nm. If it is desired to further enhance the metal corrosion resistance, the main silver layer 32 may be formed of an alloy mainly composed of silver within a range that does not reduce the reflectance. Examples of the additive material for the silver alloy include Bi, Pd, Cu, Au, Ge, Nd, Al and the like.

In the reflective layer 33, the material of the first layer 33f that comes into direct contact with the main silver layer 32 is mainly aluminum oxide. This is because in the multilayer film design for increasing the reflectance of the main silver layer 32, if a layer having a high refractive index is present in the first layer, the reflection performance may be deteriorated. Aluminum oxide is a material having a relatively low refractive index (a material having a low refractive index in a broad sense), which is desirable in terms of optical design, and has relatively good adhesion to the main silver layer 32. Materials such as LaTIO ₃ , CeO _2, Y ₂ O _{3, and} SnO ₂ used in the adhesion layer 31 have a high refractive index of 1.8 or more, which is inappropriate for thin film design as the first layer, and adhesion and stress adjustment. As a result of examination from the above viewpoint, it was found that various requirements are satisfied by the layer containing aluminum oxide. Further, it was found that there is no quality problem if the layer laminated on the first layer 33f is two or more layers using a high refractive index material and a low refractive index material in the design for the purpose of increased reflection. It was.

The polyreflection layer 33 includes at least three or more layers. The specific hyperrefractive layer 33 is a dielectric multilayer film in which a high refractive index material layer 33a and a low refractive index material layer 33b are alternately laminated on the lowermost first layer 33f, and the uppermost layer is a low refractive index material layer 33b. It is formed of a material layer 33b. The first layer 33f in contact with the main silver layer 32 can be regarded as a medium refractive index material layer in that it has a higher refractive index than the highest low refractive index material layer 33b, but in a broad sense, it has a high refractive index. In relation to the material layer 33a, it is referred to as a low refractive index material layer. The high refractive index material layer 33a has a refractive index of 1.8 or more, the low refractive index material layer 33b has a refractive index of 1.55 or less, and the first layer 33f has a refractive index of 1.55 or more. It has a refractive index of less than 1.80. The material of the low refractive index material layer 33b is selected from at least one of SiO ₂ and a mixed material in which SiO ₂ is mixed with aluminum oxide. The material of the high refractive index material layer 33a is selected from at least one of TiO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ , La TiO ₃ , ZrO ₂ , and a mixed material of these materials. The first layer 33f is formed of a material mainly composed of aluminum oxide as described above.

The high-refractive index material layer 33a and the low-refractive index material layer 33b have a thickness set according to the refractive index for each layer according to the optical design, and the thicknesses of the same refractive index material layers 33a and 33b may differ. .. When the high-refractive index material layer 33 is composed of a plurality of high-refractive index material layers 33a and a plurality of low-refractive index material layers 33b, for example, the plurality of high-refractive index material layers 33a are formed of different materials having different refractive indexes. can do. Further, the single low refractive index material layer 33b can be composed of a plurality of types of low refractive index material layers, and similarly, the single high refractive index material layer 33a is composed of a plurality of types of high refractive index material layers. You can also do it.

The reflective layer 33 may include at least one adjusting layer, similarly to the close contact layer 31. That is, the first layer 33f constituting the reflective layer 33 and the high refractive index material layer 33a above the first layer 33f can also be used as an adjusting layer for balancing the film stress. For example, the first layer 33f adjacent to the main silver layer 32 can be an adjusting layer having a relatively weak negative film stress, similarly to the first layer 31a of the adhesion layer 31. Further, the first layer 33f is subjected to a film stress after being put into a high-temperature drying environment having a relative humidity of 20% RH or less (specifically, substantially zero humidity) at an ambient temperature of 110 ° C. for 24 hours in a single layer state. The film stress after being put into a high-temperature and high-humidity environment with an ambient temperature of 85 ° C. and a relative humidity of 85% RH for 24 hours can be changed in the negative direction. Further, the high refractive index material layer 33a on the first layer 33f can be an adjusting layer having a negative film stress of a certain level or more, similarly to the second layer 31b of the adhesion layer 31. The high refractive index material layer 33a is subjected to film stress after being put into a high-temperature drying environment at an ambient temperature of 110 ° C. and a relative humidity of 20% RH or less (specifically, substantially zero humidity) for 24 hours in a single layer state. Select a film in which the film stress changes in the positive direction after being put into a high-temperature and high-humidity environment with an ambient temperature of 85 ° C. and a relative humidity of 85% RH for 24 hours.

In addition, the film stress of the entire reflective layer 33 is preferably in a state negatively larger than −50 MPa from the viewpoint of preventing cracks in a high temperature environment. In this case, the tolerance of the reflective layer 33 to the expansion and contraction of the substrate 20 is increased, and it is possible to prevent the substrate 20 from being left in a high-temperature drying environment for a long time and easily cracking.

Hereinafter, a film forming apparatus for forming an element film constituting the reflective film 30 on the surface of the work W corresponding to the substrate 20 and the like shown in FIG. 1 will be described with reference to FIG.

The illustrated film forming apparatus 100 has a vapor deposition source 51 as a film forming material source, a vapor deposition holder 52 that supports and rotates a plurality of workpieces W, and a film thickness in the vacuum vessel 59 in the meridian direction of the vapor deposition holder 52. A film thickness correction plate 54 for adjusting, an ion gun 56 for irradiating the work W with an ion beam at the time of film formation, and a neutralization gun 57 for neutralizing the ions are provided. Further, in the film forming apparatus 100, outside the vacuum vessel 59, the vapor deposition source driving unit 61 that controls the operation of the vapor deposition source 51, the holder drive unit 62 that rotationally drives the vapor deposition holder 52, the posture of the film thickness correction plate 54, etc. A correction plate drive unit 64 for adjusting the pressure, an ion gun drive unit 65 for operating the ion gun 56 and the like, a gas supply unit 66 for supplying gas to the ion gun 56 and the like, and a gas discharge unit 67 for reducing the pressure inside the vacuum vessel 59. A control unit 69 for controlling the operation of each unit constituting the film device 100 is provided.

The thin-film deposition source 51 enables vacuum-depositing of various film-forming materials, and is fixed on the stage at the bottom of the vacuum vessel 59. The vapor deposition source 51 has a container (not shown) for holding the evaporative substance, and the evaporative substance 51a in the container is heated by an electron gun or resistance heating. The vaporized material vapor EM can be injected upward from the vapor deposition source 51. The thin-film deposition source 51 is operated by the thin-film deposition source driving unit 61. A shutter 51d is attached to the vapor deposition source 51, and the injection timing of the steam EM can be arbitrarily set. When the main material of the evaporative substance 51a is silver as in the case of film formation of the main silver layer 32 using an alloy, the proportion of additives present in the thin film after film formation is determined by heating due to the difference in evaporation temperature. It can be adjusted by the temperature and the timing of opening and closing the shutter 51d.

The vapor deposition holder 52 is arranged above the vapor deposition source 51 in the vacuum vessel 59. The vapor deposition holder 52 has a dome shape or a conical shape as a whole, and holds a large number of work Ws via a large number of support jigs 52a. The vapor deposition holder 52 is rotated around the shaft Z by the holder drive unit 62 so that each work W is periodically opposed to the vapor deposition source 51. The vapor deposition holder 52 tilts the surface Wa of the work W with respect to the vapor deposition source 51 by a predetermined angle α (specifically, 45 °). This is in consideration of the fact that the angle of incidence of the light beam on the reflecting film 30 is the angle α in the product in which the silver reflecting mirror 10 is incorporated.

The film thickness correction plate 54 is arranged between the vapor deposition source 51 and the vapor deposition holder 52. The posture of the film thickness correction plate 54 in the vacuum container 59 is controlled by the correction plate drive unit 64. The film thickness correction plate 54 can be operated from the outside by the mechanical mechanism 54a, can be raised and lowered as appropriate so that the inclination of the axis X increases or decreases, and is further rotated around the axis X if necessary. You can also. When the film thickness correction plate 54 is raised and placed above the vapor deposition source 51, the portion behind the film thickness correction plate 54 in the support jig 52a is not vapor-deposited, and the film thickness difference with respect to the warp direction of the vapor deposition holder 52. Can be adjusted.

The ion gun 56 extracts ions in the plasma by applying a voltage or the like and emits them to the outside of the ion gun 56. Specifically, the ion gun 56 ionizes the gas supplied from the gas supply unit 66, and applies a beam voltage between the anode 56a and the cathode 56b of the ion gun 56. The ion gun 56 approaches and passes an ionized gas (for example, positive ions) toward the cathode 56b side and discharges it into the vacuum vessel 59 as an ion beam IB. The emitted ion beam IB irradiates the surface Wa of the work W supported by the vapor deposition holder 52. As a result, the surface Wa of the work W is activated or the thin film of the surface Wa of the work W is rearranged, so that the thin film of the surface Wa of the work W can be made denser while being more closely adhered.

Since the ion beam IB is irradiated, the gas supplied from the gas supply unit 66 to the ion gun 56 can be an inert gas to which a reactive gas is added. As the inert gas, for example, various gases such as argon (Ar), nitrogen (N ₂ ), and helium (He), and a mixed gas thereof can be used. Further, as the reactive gas, for example, oxygen (O ₂ ) or the like can be used.

The neutralization gun 57 is for neutralizing the ions in the ion beam IB and suppressing the influence of the electric field distribution. A gas for ionization is introduced into the neutralization gun 57 from the gas supply unit 66, and the introduced gas is ionized. When the electrons generated by ionization are released into the vacuum vessel 59, the gas molecules ionized by the ion gun 56 and released to the vapor deposition holder 52 side are neutralized by the electrons. A neutralization grid may be used instead of the neutralization gun 57.

In addition, the gas discharge unit 67 decompresses the inside of the vacuum container 59, and the oxygen introduction port 58 provided at the bottom of the vacuum container 59 supplies oxygen gas or the like into the vacuum container 59. An auto pressure controller (not shown) is provided between the oxygen inlet 58 and the gas discharge unit 67, so that the oxygen pressure in the vacuum vessel 59 and the like can be made substantially constant during film formation.

The thin-film deposition source driving unit 61 operates the thin-film deposition source 51 to inject the vapor EM of the evaporated substance upward. The holder drive unit 62 rotates the vapor deposition holder 52 around the central axis Z during the formation of the vapor EM by the vapor deposition source 51. The correction plate driving unit 64 adjusts the rotation and other postures of the film thickness correction plate 54 during the vapor deposition by the vapor deposition source 51. During the formation of the steam EM by the vapor deposition source 51, the ion gun drive unit 65 operates the ion gun 56 to irradiate the surface Wa of the work W with the ion beam IB and operates the neutralization gun 57 to neutralize the periphery of the work W. Do. The control unit 69 operates the vapor deposition source 51 via the vapor deposition source drive unit 61 while rotating the vapor deposition holder 52 by the holder drive unit 62 to form a thin film of the evaporative substance on the surface Wa of the work W. At this time, the control unit 69 operates the ion gun 56 and the like via the ion gun driving unit 65 to make the thin film of the evaporative substance formed on the surface Wa of the work W have high adhesion to the work W. , Make the thin film of such evaporative material dense.

The film forming apparatus 100 described above enables vapor deposition by an ion assist method (that is, ion beam assisted vapor deposition), and forms a film of the first layer 31a and the second layer 31b mainly constituting the adhesion layer 31. Used for. By adjusting the degree of irradiation of the ion beam IB, the density or density of the first and second layers 31a and 31b can be adjusted. In addition, the element film and the main silver layer 32 constituting the brightening reflection layer 33 can also be formed by using the film forming apparatus 100. In particular, the low refractive index material layer 33b and the main silver layer 32 of the reflective layer 33 can be easily formed by using a normal thin-film deposition apparatus that does not use an ion gun 56 or the like. When laminating a plurality of types of element films constituting the reflective film 30, the film can be sequentially formed by a plurality of film forming devices 100 having different vapor deposition substances, but the vapor deposition substances are formed in the same film forming device 100. It is also possible to sequentially perform film formation while switching between.

Hereinafter, an environmental test apparatus for inspecting the silver reflector 10 shown in FIG. 1 will be described with reference to FIG.

The illustrated environmental test device 200 has a humidity control chamber 71 having a heat insulating wall and forming a closed space, an air circulation fan 73, an auxiliary temperature control unit 74 for performing auxiliary temperature control, and indoor temperature and humidity. It includes a temperature / humidity sensor 75 for measurement, an air adjusting unit 77 for keeping the temperature and humidity in the humidity control chamber 71 constant, and a control device 79 for controlling them. The work W2 tested by the environmental test apparatus 200 may be a finished silver reflector 10, but the first layer 31a, the second layer 31b, and the like constituting the adhesion layer 31 are independently formed on the substrate 20. In some cases, the film is formed in.

The humidity control chamber 71 stores a plurality of work W2 in a state of being supported by the shelf 71a. At that time, the temperature and humidity in the humidity control chamber 71 are monitored by the temperature / humidity sensor 75 while the air circulation fan 73 circulates the atmosphere in the humidity control chamber 71. The auxiliary temperature control unit 74 auxiliary heats or cools the air around the work W2 based on the detection result of the temperature / humidity sensor 75.

The air adjusting unit 77 once takes in the air in the humidity control chamber 71 and sends it out into the humidity control chamber 71 as air having a target temperature and humidity. The air adjusting unit 77 makes it possible to monitor changes in the characteristics of the silver reflector 10 or the like in a high temperature or high temperature and high humidity environment. Specifically, the environment achieved by the air adjusting unit 77 includes, firstly, a high-temperature drying environment having an ambient temperature of 110 ° C. and a humidity of substantially zero, and secondly, a relative humidity of 85% at an ambient temperature of 85 ° C. A high temperature and high humidity environment of RH is included, and a high temperature and dry environment with an ambient temperature of 85 ° C. and almost zero humidity is also included. The high-temperature drying atmosphere or the high-temperature and high-humidity atmosphere formed by the air adjusting unit 77 is homogenized by the air circulation fan 73 and sent to the periphery of the work W2.

The control device 79 appropriately operates the air adjusting unit 77 and the like to hold the work W2 in a first environment (that is, in a high-temperature drying environment where the ambient temperature is 110 ° C. and the humidity is substantially zero) for 24 hours, and then the work. W2 is held in a second environment (that is, in a high temperature and high humidity environment with an atmospheric temperature of 85 ° C. and a relative humidity of 85% RH) for 24 hours. The operation of holding the work W2 in the first environment for 24 hours and then switching to the second environment and holding it for 24 hours is also called a humidity increasing type environmental test. By operating the air adjusting unit 77, the control device 79 can also hold the work W2 in a high temperature drying environment or a high temperature and high humidity environment in a stable state for a long period of time such as 1000 hours.

The temperature of the work W2 can be gradually changed at the start of the first environment and at the end of the second environment. Further, when switching from the first environment to the second environment, the environment test apparatus 200 itself can be changed. Further, when switching from the first environment to the second environment, it is possible to perform an operation such as temporarily returning to room temperature to stabilize the state.

Further, the work W2 tested by the illustrated environmental test apparatus 200 is not limited to the silver reflecting mirror 10 of the product, and a specific reflective layer or a constituent layer constituting the reflective film 30 is independently formed on the substrate 20. You can also do it.

Hereinafter, a measuring device for measuring the film stress and the like of the reflective film 30 constituting the silver reflecting mirror 10 shown in FIG. 1 will be described with reference to FIG.

The illustrated stress measuring device 300 includes a pair of support members 81 that support both ends of the strip-shaped work W2 from below, a laser light source 82 that irradiates the surface Wa of the work W2 with laser light P1 from vertically above, and the work W2. It is provided with a reflected light sensor 83 that detects the laser light P2 reflected by the surface Wa of the above, and a control device 85 that controls the operation of the reflected light sensor 83 and the like.

The pair of support members 81 support the work W2 at two points separated by a length L. Here, the tops of both support members 81 have the same height, and the work W2 extends in the horizontal direction when bending is ignored. The laser light source 82 is arranged vertically above one of the support members 81, emits laser light P1 toward the support member 81, and forms a light spot on the surface Wa of the work W2. The reflected light sensor 83 detects the laser light P2 which is the specularly reflected light from the light spot on the surface Wa of the work W2. The reflected light sensor 83 has a support portion (not shown) and the like, and can move the laser beam P2 to a height position where it can be detected most strongly, and can measure the height H. When the work W2 is slightly bent in an arc shape, the radius of curvature R of the bent work W2 is approximately given by 2H, and the incident point of the laser beam P1 seen from the origin O of the curvature of the work W2. The opening angle θ of is approximately given by L / 4H using the length L of the chord. The control device 85 calculates the film stress of the thin film formed on the surface Wa of the work W2 based on the opening angle θ of the work W2.

Stoney's equation was used for the calculation of the film stress performed by the control device 85. That is, in the strip-shaped work W2, when the thickness of the substrate 20 of the work W2 is D and the film thickness of the reflective film F of the work W2 is d, the film thickness d is extremely thin and D >> d. .. At this time, the stress σ of the reflective film F is expressed by the following equation using the radius of curvature R of the work W2.
σ = (Es × D ² ) / [6d (1-v) R]
However, Es is the Young's modulus of the substrate 20, and v is the Poisson's ratio of the substrate 20.

Here, the relationship between the length L of the chord and the radius of curvature R is R = L / 2θ, and when the opening angle θ is extremely small, an approximation of 2θ≈2sinθ is allowed, so that the stress σ is
σ ≒ (Es × D ² ) / [6d (1-v) L / (2sinθ)]
Can be approximated to.

However, the opening angle θ is obtained as the deflection angle of the reflected laser beam P2 as long as the work W2 is considered to be bent in an arc shape, but for convenience of calculation, the change in stress before and after the film formation of the reflective film F is obtained. Is considered to be the film stress, and the film stress can be expressed by the following equation using the difference Δθ between the opening angles before and after the coating.
σ ≒ (Es × D ² ) / [6d (1-v) L / (2sinΔθ)]

The work W2 measured by the stress measuring device 300 shown in the figure measures the film stress of the reflecting film 30 or its constituent elements in the silver reflecting mirror 10 of the product, and has the same shape as the silver reflecting mirror 10 of the product. It does not have to be, and the material of the substrate 20 can also be different from the substrate material of the silver reflector 10 of the product. However, it can be said that the measurement of the film stress of the reflective film 30 or its constituent elements tends to be relatively accurate when it is performed in a situation close to that of the silver reflector 10 of the product.

Hereinafter, a method for manufacturing and an inspection method for the silver reflector 10 shown in FIG. 1 will be described. First, the substrate 20 having the optical surface 21 is prepared, and the first layer 31a and the second layer 31b are sequentially formed on the optical surface 21 by using the film forming apparatus 100 shown in FIG. 2 to complete the adhesion layer 31. Next, the main silver layer 32 is formed on the adhesion layer 31 by using the same film forming apparatus 100. Then, the reflective layer 33 is formed on the main silver layer 32 by using the same film forming apparatus 100. As a result, the silver reflecting mirror 10 having the reflecting film 30 provided on the substrate 20 is completed. A test piece (work W2) for environmental test is also prepared. In this test piece, for example, a reflective film 30 is formed on a strip-shaped substrate 20 under the same conditions. Further, only the first layer 31a, which is one of the adhesion layers 31, is formed on the strip-shaped substrate 20, and only the second layer 31b, which is the other of the adhesion layers 31, is formed on the strip-shaped substrate 20. Also prepare things as test pieces. Further, a strip-shaped substrate 20 on which only the reflective layer 33 is formed is also prepared as a test piece.

Next, the completed silver reflector 10 or test piece (work W2) is set in the environmental test apparatus 200 and held in a high-temperature drying environment (first environment) at an ambient temperature of 110 ° C. and a humidity of substantially zero for 24 hours. It is kept in a hot and humid environment (second environment) with an ambient temperature of 85 ° C. and a relative humidity of 85% RH for 24 hours. That is, a humidity increasing type environmental test is performed on the test piece (work W2).

After that, the film stress is measured for the test piece (work W2) that has not undergone the humidity increase type environmental test and the test piece (work W2) that has undergone the humidity increase type environmental test. That is, the test piece (work W2) is set in the stress measuring device 300, and the stress of the thin film on the surface of the test piece is measured. When the stress of the thin film on the surface of the test piece satisfies a predetermined condition, it is judged that the silver reflector 10 completed under the same conditions as the test piece has sufficient resistance to an environment such as high temperature and high humidity. Will be done. Specifically, for the test piece (work W2) having the same structure as the completed silver reflector 10, the film stress of the reflective film 30 after film formation is in the range of +100 MPa to -100 MPa, and the first It is important that the film stress of the reflective film 30 after being held in the above environment for 24 hours is in the range of +100 MPa to -100 MPa as a premise for ensuring the quality of the silver reflector 10. Further, the film stress of the reflective film 30 after the test piece (work W2) was put into the second environment and then put into a high temperature and high humidity environment of 85 ° C. and 85% RH for 24 hours was increased from +100 MPa to -100 MPa. It also determines whether it is within the range. Further, as a result of holding the test piece (work W2) having the same structure as the completed silver reflector 10 in the first environment for 24 hours and then in the second environment for 24 hours, the film stress When the change difference as an absolute value of the value is 40 MPa or less, it is determined that deterioration such as peeling of the reflective film 30 can be prevented and high reflection characteristics can be maintained even in a high temperature and high humidity environment.

Further, among the test pieces (work W2), the test piece in which the first layer 31a of the adhesion layer 31 is formed of a single layer and the test piece in which the second layer 31b of the adhesion layer 31 is formed of a single layer are also described above. The stress of the thin film on the surface of the test piece is measured before and after the humidity increasing type environmental test in which the test piece is held in the first environment for 24 hours and then held in the second environment for 24 hours. As a result of holding the lower first layer 31a in the first environment for 24 hours and then holding it in the second environment for 24 hours, the difference in change as the absolute value of the film stress value is negative (compressive stress). In the case of (direction), it is determined that high reflection characteristics can be maintained by preventing deterioration such as peeling of the reflective film 30 even in a hot and humid environment. Further, as a result of holding the upper second layer 31b in the first environment for 24 hours and then holding it in the second environment for 24 hours, the difference in change as the absolute value of the film stress value is positive (pull). In the case of (stress direction), it is determined that high reflection characteristics can be maintained by preventing deterioration such as peeling of the reflection film 30 even in a hot and humid environment.

In addition, using the environmental test apparatus 200, the completed silver reflector 10 or the test piece (work W2) is placed in (1) a high-temperature drying environment (first environment) at an ambient temperature of 110 ° C. and a humidity of almost zero. Test to hold for 1000 hours, (2) Test to hold for 1000 hours in a high temperature and humidity environment (second environment) with relative humidity of 85% RH at ambient temperature 85 ° C, (3) High temperature and dry environment with ambient temperature of 85 ° C and almost zero humidity Perform a test of holding under (third environment) for 1000 hours. These tests are materials for directly judging the durability of the silver reflector 10 in terms of appearance and optical performance.

〔Example〕
Hereinafter, specific examples of the silver reflector according to the present invention will be described.

As the film forming apparatus 100, a model GENER-1300 manufactured by OPTORUN Co., Ltd. equipped with an ion gun and the like was used.

As the material of the substrate 20, polycarbonate H-3000R manufactured by Mitsubishi Engineering Plastics Co., Ltd. was used, and a material formed to a thickness of 3 mm with a diameter of 30 mm was used as a film forming target, that is, a work W.

Since the surface to be deposited of the expected actual product is located at a vapor deposition incident angle of 45 degrees, the substrate 20 is installed in a state of being tilted 45 degrees with respect to the surface orthogonal to the vapor deposition source 51 or the support surface of the vapor deposition holder 52. Was done.

Among the reflective films, the adhesion layer uses the ion assist method for the purpose of further enhancing the moisture blocking effect and adjusting the overall stress for the aluminum oxide layer, which has good adhesion to the substrate and has a high moisture blocking effect. The film was formed. Next, a film of LaTIO ₃ (Substance H4) having good adhesion to the main silver layer was formed. LaTIO ₃ (Substance H4) has a function of blocking water by itself, but the ion assist method was used for the purpose of further enhancing the blocking effect and adjusting the overall stress. Aluminum oxide and LaTIO ₃ (Substance H4) were formed with a film thickness of 40 nm to 60 nm from the viewpoint of stress adjustment, but if the film thickness is in the range of 10 nm to 200 nm, even if the thickness is changed to adjust the total stress. , It is known that there is no significant effect on environmental resistance.

Next, a main silver layer was formed on the LaTIO ₃ (Substance H4) film. In Experimental Examples 1 to 8, sterling silver was formed. Further, in Example 9, a film was formed using an alloy material containing 1% of bismuth (Bi) in silver (Ag) (specifically, an Ag-Bi material (manufactured by Kobelco Research Institute)). Further, in Example 10, a film was formed using an alloy material containing 0.25% bismuth in silver (specifically, an Ag-Bi material (manufactured by Kobelco Research Institute)). The film thickness of the main silver layer is 60 nm, but there is no problem whether it is thin or thick as long as the reflectance can be secured. Further, although the resistance heating method was used for the film formation of the main silver layer, vapor deposition with an electron gun may be performed.

Next, a reflective layer was formed on the main silver layer. In the embodiment, two types of multilayer film designs are implemented for stress adjustment. In the first type of design, an aluminum oxide layer having a refractive index of 1.55 to 1.65 is formed as a lower low refractive index material layer at 120 nm, and then a high refractive index layer having a refractive index of 1. A LaTIO ₃ (Substance H4) layer of 8 to 2.2 was formed to a thickness of 80 nm, and finally, a SiO ₂ layer having a refractive index of 1.42 to 1.5 was formed to a thickness of 30 nm mainly for the purpose of scratch resistance. It has a three-layer structure as a whole. In the second type of design, an aluminum oxide layer having a refractive index of 1.55 to 1.65 is formed to form a film at 35 nm, and then as a high refractive index layer, LaTIO ₃ (Substance) having a refractive index of 1.8 to 2.2 is formed. The H4) layer was formed at 75 nm, then the SiO ₂ layer with a refractive index of 1.42 to 1.5 was formed at 20 nm, then the LaTIO ₃ (Substance H4) layer was formed at 80 nm, and finally the scratch resistance was formed. For the main purpose of property, _two layers of SiO having a refractive index of 1.42 to 1.5 were formed at 30 nm, and a total of five layers was formed. The effect of increased reflection was observed in both the first type design and the second type design, and the reflectance with respect to P-polarized light incident at 45 degrees at a wavelength of 870 nm satisfied 95% or more.

In order to evaluate the film stress of the manufactured silver reflector 10, not only the substrate 20 having a diameter of 30 mm and a thickness of 3 mm but also a measurement substrate (test piece) for measuring the film stress was prepared. A glass material D263 manufactured by Schott AG was used as the measurement substrate, and a thin strip-shaped glass substrate having a thickness of 0.1 mm and a thickness of 50 mm × 10 mm was processed into a film forming target, that is, a work W. Since a stable physical property value of the substrate is required for the measurement of the film stress, a stable glass glass material that is not easily affected by water absorption or other external influences was used. Similar to the substrate 20 of the silver reflector 10, the film stress measuring substrate was also installed in a state of being tilted 45 degrees with respect to the surface orthogonal to the vapor deposition source 51 or the support surface of the vapor deposition holder 52, and the film was formed.

上記表１において、「材料条件」欄は、反射膜を構成する膜材料を意味し、「Ａｌ２Ｏ３−Ａ」〜「Ａｌ２Ｏ３−Ｆ」は、成膜条件が異なる酸化アルミニウム膜を意味する。「Ｈ４」は、Ｍｅｒｃｋ社製のＬａＴｉＯ_３（Substance H4）を意味し、「ＳｉＯ２」は、酸化シリコン膜又はシリカ膜を意味し、「Ａｇ」は、主銀層を意味する。「Ｍｅｔｈｏｄ」欄において、「ＥＢ」は電子ビーム蒸着による成膜を意味し、「ＥＢ＋ＩＡＤ」は、イオンアシストタイプの電子ビーム蒸着を意味し、「ＲＨ」は、抵抗加熱による成膜を意味する。「Ｏ２−ＡＰＣ（Ｐａ）」欄は、成膜中における酸素分圧の調整値を意味し、例えばＡｌ２Ｏ３−Ａの場合、酸素分圧が２．００×１０^−２Ｐａに設定されたことが示されている。「ｒａｔｅ（オングストローム／ｓｅｃ）」欄は、成膜速度を意味する。なお、表１には記載していないが、成膜開始時の真空度は２．０×１０^−３Ｐａであり、成膜に際して基板の加熱は行わなかった。Table 1 below summarizes the film formation conditions.
[Table 1]

In Table 1 above, the "material condition" column means the film material constituting the reflective film, and "Al2O3-A" to "Al2O3-F" mean aluminum oxide films having different film forming conditions. "H4" means LaTIO ₃ (Substance H4) manufactured by Merck & Co., "SiO2" means a silicon oxide film or a silica film, and "Ag" means a main silver layer. In the "Method" column, "EB" means film formation by electron beam deposition, "EB + IAD" means ion-assisted electron beam deposition, and "RH" means film formation by resistance heating. The "O2-APC (Pa)" column means the adjustment value of the oxygen partial pressure during film formation. For example, in the case of Al2O3-A, the oxygen partial pressure was set to 2.00 × ^10-2 Pa. It is shown. The "rate (angstrom / sec)" column means the film formation rate. Although not shown in Table 1, the degree of vacuum at the start of film formation was 2.0 × 10 ^-3 Pa, and the substrate was not heated during film formation.

The "IAD" column indicates the conditions for ion assist, "Voltage (V)" means the beam voltage of the ion gun 56, and "Current (mA)" means the beam current of the ion gun 56. , "Acc (V)" means an accelerating voltage. “O2 (GAS1) (SCCM)”, “Ar (GAS2) (SCCM)”, and “Ar (GAS3) (SCCM)” indicate the supply flow rate of oxygen or argon. Here, Ar (GAS2) indicates the amount of the argon gas component supplied to the ion gun 56, and Ar (GAS3) indicates the amount of the argon gas supplied to the neutralization gun 57. As for the materials "Al2O3-A", "Al2O3-B", "SiO2", and "Ag", the value in the "IAD" column is blank because the ion-assisted film is not formed.

The refractive indexes of the films obtained from the above "Al2O3-A" to "Al2O3-F" were 1.5768, 1.5763, 1.588, 1.576, 1.5897, and 1.6102, respectively. .. That is, the refractive index of the aluminum oxide layer using the ion assist method is in the range of 1 to 1.025 times the refractive index when the film is formed without using the ion assist method.

［表３］

表２及び表３において、層番号は、基板からの層の順番を意味する。なお、基板は、基本的にポリカーボネート（ＰＣ）製であるが、膜応力測定用の測定基板（テストピース）の場合、硝材Ｄ２６３製となる場合もある。Table 2 below describes the film structures of the reflective films of Examples 1 to 10 and Comparative Examples 1 to 4, and Table 3 below shows the film elements constituting the reflective films of Examples and Comparative Examples. It is a summary of the film thickness of.
[Table 2]

[Table 3]

In Tables 2 and 3, layer numbers mean the order of layers from the substrate. The substrate is basically made of polycarbonate (PC), but in the case of a measuring substrate (test piece) for measuring film stress, it may be made of glass material D263.

表４において、「８５℃ＤＲＹ−１０００Ｈ」は、雰囲気温度８５℃で湿度略ゼロの高温乾燥環境に１０００時間保持されたことを意味し、「１１０℃ＤＲＹ−１０００Ｈ」は、雰囲気温度１１０℃で湿度略ゼロの高温乾燥環境に１０００時間保持されたことを意味し、「８５度８５％−１０００Ｈ」は、雰囲気温度８５℃で相対湿度８５％ＲＨの高温多湿環境に１０００時間保持されたことを意味する。Table 4 below summarizes the results of environmental resistance tests for the silver reflectors of Examples 1 to 10 and Comparative Examples 1 to 4.
[Table 4]

In Table 4, "85 ° C. DRY-1000H" means that the product was kept in a high-temperature drying environment at an ambient temperature of 85 ° C. and a humidity of substantially zero for 1000 hours, and "110 ° C. DRY-1000H" means that the ambient temperature was 110 ° C. It means that it was held for 1000 hours in a high temperature and dry environment with almost zero humidity, and "85 degrees 85% -1000H" means that it was held for 1000 hours in a high temperature and high humidity environment with an ambient temperature of 85 ° C and a relative humidity of 85% RH. means.

The "appearance determination" is the result of the appearance measurement, and visual observation under a fluorescent lamp, normal stereomicroscopic observation, and 1000 times microscopic observation with VHX2000 manufactured by KEYENCE Corporation were performed. The main types of appearance defects are cracks, film floating, cloudiness, and discoloration. However, cloudiness and discoloration are excluded from the target because differences appear depending on the reflectance, and cracks and film floating are evaluated items. And said. In other words, regarding the above cracks and film floating, those that pass are marked with ○, those with relatively shallow cracks of several mm or less are marked with △, and those that fail with either one are marked with ×. Evaluation was performed. As for cracks, those in which no cracks were visually observed under a fluorescent lamp were accepted. Regarding the film float, it is accepted when the number of circular floats having a diameter of about 100 μm is 30 or less in a silver reflector having a diameter of 30 mm. As a form of film floating, in addition to the circular film floating, there is a string-shaped film floating as observed in a normal vapor-deposited film, but this is also rejected. The criteria for passing these appearances are those that do not cause any problems in optical performance by actually measuring and evaluating products incorporating a silver reflector, but they can also be used as criteria used in general catadioptric systems. It is considered to be well within the permissible or applicable range.

“Reflectance” is the result of reflectance measurement, and the P-polarized light reflected at 45 degrees in the wavelength band of 870 nm ± 30 nm was measured using a spectrophotometer MCPD3000 manufactured by Otsuka Electronics Co., Ltd. This is a shape that matches the form in which the silver reflector is incorporated into the product. In the reflectance measurement, those showing a reflectance of 95% or more as a whole in the band were evaluated as ◯, and those showing a reflectance of less than 95% were evaluated as x. The value of 95% assumes a catadioptric system as a form of incorporation into the product, and is a sufficiently acceptable value for the optical performance of the target product group. Also, in general, a reflector using silver has a very high reflectance, and 95% can be said to be a satisfactory value.

The "tape test" is an experiment in which a tape with an adhesive surface is once attached to a reflective film and then peeled off. The one in which the reflective film is maintained without peeling is marked with a circle, and the one in which the reflective film is peeled off is marked with a cross. Evaluation was performed.

Regarding the determination of the appearance and reflectance of "85 degree DRY1000H" after the high temperature drying test, not only Examples 1 to 10 but also all of Comparative Examples 1 to 4 passed (marked with ◯).

Further, regarding the determination of the appearance and the reflectance of "110 ° C. DRY-1000H" after the high temperature drying test, Examples 6 to 10 passed without any problem (marked with a circle), and Examples 1 to 5 were several mm. Shallow cracks were observed below, but the level was at a level (△ mark) that was not a problem in practical use. In addition, 1 to 4 of the comparative example were also passed (○ mark) or a level at which there was no problem in practical use (Δ mark).

Regarding the appearance judgment, the reflectance, and the judgment of the tape test after the high temperature and high humidity test of "85 degrees 85% -1000H", all of Examples 1 to 10 passed (marked with ◯). On the other hand, in Comparative Example 1, there is a problem (x mark) in the result of appearance judgment and reflectance, in Comparative Examples 2 and 3, there is a problem (x mark) in the result of appearance judgment, and in Comparative Example 4, there is a tape test. There was a problem (x mark) in the result of.

Table 5 below summarizes the results of the film stress test for the silver reflectors of Examples 1 to 10 and Comparative Examples 1 to 4.
[Table 5]

表５において、第１欄は、密着層を構成する第１層のＡｌ_２Ｏ_３を基板上に単層で作製した場合について、膜応力（単位「ＭＰａ」）の環境変化を試験した結果を示す。まず、第１工程（「一週間」）では、テストピースを室温で一週間放置して膜状態を安定させた。次に、第２工程（「１１０℃２４Ｈ」）では、テストピースを雰囲気温度１１０℃で湿度略ゼロの高温乾燥環境に２４時間保持して反射膜を一旦乾燥させた。最後に、第３工程（「８５℃８５％２４Ｈ」）では、テストピースを雰囲気温度８５℃で湿度８５％の高温高湿環境に２４時間保持して反射膜に加湿を行った。「差分」欄は、「１１０℃２４Ｈ」の処理後の膜応力から「８５℃８５％２４Ｈ」の処理後の膜応力を引いた値である。この差分は、膜応力の変化量の符号を反転させたものとなっている。つまり、実施例１の場合、２４時間の高温乾燥環境から２４時間の高温高湿環境への切り替えによって、密着層第１層の膜応力が１３７ＭＰａだけ減少し、膜応力の変化量は、負（圧縮応力）方向に相当するものとなっている。For reference, Table 6 summarizes the results of the film stress test for each layer (see Table 1) constituting the example of the reflective film 30. For example, the aluminum oxide films "Al2O3-A" to "Al2O3-F" constitute the first layer 31a of the adhesion layer 31 and the first layer 33f of the reflective layer 33 in Examples and Comparative Examples.
[Table 6]

In Table 5, the first column shows the results of testing the environmental change of the film stress (unit: "MPa") when the first layer Al ₂ O ₃ constituting the adhesion layer was prepared as a single layer on the substrate. Shown. First, in the first step (“one week”), the test piece was left at room temperature for one week to stabilize the film state. Next, in the second step (“110 ° C. 24H”), the test piece was held in a high-temperature drying environment at an ambient temperature of 110 ° C. and a humidity of substantially zero for 24 hours to temporarily dry the reflective film. Finally, in the third step (“85 ° C. 85% 24H”), the test piece was kept in a high temperature and high humidity environment with an ambient temperature of 85 ° C. and a humidity of 85% for 24 hours to humidify the reflective film. The "difference" column is a value obtained by subtracting the film stress after the treatment of "85 ° C. 85% 24H" from the film stress after the treatment of "110 ° C. 24H". This difference is obtained by reversing the sign of the amount of change in film stress. That is, in the case of Example 1, the film stress of the first layer of the adhesion layer is reduced by 137 MPa by switching from the high temperature drying environment for 24 hours to the high temperature and high humidity environment for 24 hours, and the amount of change in the film stress is negative ( It corresponds to the compressive stress) direction.

In Table 5, the second column shows the results of testing the environmental change of the film stress (unit "MPa") in the case where the second layer LaTIO ₃ (H4) constituting the adhesion layer is prepared as a single layer on the substrate. Is shown. The meanings of "one week" (first step), "110 ° C. 24H" (second step), "85 ° C. 85% 24H" (third step), and "difference" are the same as in the first column. In the case of Example 1, the film stress of the second layer of the adhesion layer increased by 29 MPa by switching from the high temperature drying environment for 24 hours to the high temperature and high humidity environment for 24 hours, and the amount of change in the film stress was positive ( It corresponds to the tensile stress) direction. The arrows in the table mean that they have the same values as in the left column.

The third column shows the environmental change in film stress (unit "MPa") when only the reflective layer (consisting of Al ₂ O ₃ , LaTIO ₃ (H4), and SiO ₂ ) is produced as a multilayer film on the substrate. The results of the test are shown. The meanings of "one week" (first step), "110 ° C. 24H" (second step), "85 ° C. 85% 24H" (third step), and "difference" are the same as in the first column. In the case of Example 1, the film stress of the reflective layer is reduced by 116 MPa by switching from the high temperature drying environment for 24 hours to the high temperature and high humidity environment for 24 hours, and the amount of change in the film stress is negative (compressive stress). ) It corresponds to the direction.

The fourth column shows the result of testing the environmental change of the film stress (unit "MPa") in the case where the entire reflective film is formed as a multilayer film on the substrate. The meanings of "one week" (first step), "110 ° C. 24H" (second step), "85 ° C. 85% 24H" (third step), and "difference" are the same as in the first column. In the case of Example 1, by switching from the high temperature drying environment for 24 hours to the high temperature and high humidity environment for 24 hours, the total film stress is reduced by 18 MPa, and the amount of change in the film stress is in the negative (compressive stress) direction. It is equivalent.

Regarding the results of the above stress measurements, the film stress was 100 MPa or less in "one week" (first step), "110 ° C. 24H" (second step), and "85 ° C. 85% 24H" (third step). Is the criterion for passing. This is because, for example, when it exceeds 100 MPa with respect to the assumed product, the PV value of the optical surface exceeds the allowable range of optical performance. For example, when a film is formed on one side of a polycarbonate having a diameter of 40 mm and a wall thickness of 3 mm as in the embodiment, the amount of deformation due to a film stress of 100 MPa is about 1 μm. Since this amount of deformation changes depending on the wall thickness, the material of the base material, etc., the allowable range depends on the product, but as a general optical system, it is natural that the film stress should be as small as possible. At least, for mirrors used in precision catadioptric systems, it is desirable that the film stress be adjusted to 100 MPa or less.

The film stress is compared not only when the entire reflective film is formed as in the fourth column but also when a part of the reflective film is formed as in the first to third columns. It is desirable that the target is low.

Summarizing the results of the film stress test, with respect to the state one week after the film formation, Examples 1 to 10 and Comparative Examples 1 to 3 are films in which the stress value of the entire reflective film is close to 0 and the surface deformation can be reduced. It was. On the other hand, in Comparative Example 4, the film stress was very large, and the stress value was such that surface deformation was a concern. It is considered that this is because the film forming condition of Al ₂ O ₃ with increased reflection in Comparative Example 4 was due to the use of strong ion assist.

As for the changes after the film was put into "110 ° C. 24H" (second step), in Examples 1 to 5, the film stress was in the positive direction, as compared with the state one week after the film formation, in Examples 6 to 6. No. 10 was found to change the film stress in the negative direction. This result is considered to be significantly affected by the reflective layer, and in particular, in Examples 6 to 10, the film thickness of Al ₂ O ₃ used in the reflective layer is thin, so that LaTiO ₃ (H4) ), It can be judged that it was probably affected by the film stress.

As for the changes after being charged into "85 ° C. 85% 24H" (third step), in Examples 1, 3, 4, 6 to 10 as compared with "110 ° C. 24H" (second step), the films It was found that the stress changed in the negative direction, and in Examples 2 and 5, the film stress changed in the positive direction. It is considered that this is influenced by the film forming conditions of Al ₂ O ₃ , which is the first layer of the adhesion layer. Here, as a factor that the conditions 8 to 10 which are the same conditions for the adhesion layer as those of Examples 2 and 5 did not change in the positive direction, in Examples 8 to 10 as opposed to Examples 2 and 5. It is considered that the difference in the layer structure of the hyperreflective film used has an effect.

Looking at the difference between the above "110 ° C. 24H" (second step) and "85 ° C. 85% 24H" (third step), it was found that the absolute values of Examples 1 to 10 were 40 MPa or less. It was. On the other hand, in Comparative Examples 1 to 3, it was 40 MPa or more. In Examples 1 to 10, the absolute value of the difference in film stress is 40 MPa, which means that when the change in film stress is in the negative direction (compressive stress side), the absolute value of the amount of change is 40 MPa or less. In addition, when the change in film stress is in the positive direction (tensile stress side), the absolute value of the amount of change is 40 MPa or less. In Comparative Example 4, the absolute value of the difference in film stress is 40 MPa or less, but the original film stress is very large, and there is a concern about surface deformation.

Considering the above results, the film stress after 110 ° C. 24H treatment held in a high temperature dry state for one day and the film stress after 85 ° C. 85% 24H treatment held in a high temperature wet state for one day are complicated at the multi-layer level. It was found that the film deterioration due to the environmental change can be prevented by realizing the state of the layer structure in which the fluctuation is small.

In the prior art, the density of the layer and the material composition were mentioned, but even if the same material is used, reducing the stress against environmental changes is an important condition for obtaining a good reflective film. I found out that there is. On the other hand, as in Comparative Example 4, if some strong ion assist is used, the amount of change in the film stress becomes small and the environmental resistance is improved, but the film stress becomes too strong and surface deformation may occur. Do you get it. That is, in order to obtain a reflective film with less peeling and a decrease in reflectance while suppressing surface deformation, (1) the film stress after film formation of the reflective film is in the range of +100 MPa to -100 MPa, (2). The absolute value of the amount of change between the film stress value after being put into a high temperature and dry environment of 110 ° C. for 24 hours and the film stress value after being put into a high temperature and high humidity environment of 85 ° C. and 85% RH for 24 hours is 40 MPa or less. It turns out that it is important that each condition of being met is met. Further, (3) the film stress after the reflective film is put into a high temperature drying environment at 110 ° C. for 24 hours is in the range of +100 MPa to -100 MPa, and (4) the reflection after being put into a high temperature drying environment at 110 ° C. It is also important that the membrane stress after the membrane is placed in a hot and humid environment at 85 ° C. and 85% RH for 24 hours is in the range of +100 MPa to -100 MPa.

Here, the main points of the present invention will be described. For example, in Patent Document 2, by sandwiching aluminum oxide having high density with respect to the silver film from both sides, the effect of improving the environmental resistance and the upper layer such as TiO ₂ and SiO ₂ formed on the layer are formed. On the other hand, it was said that the stress balance would be maintained and the adhesion would be ensured. However, as a result of examination by the inventor of the present application, it has become clear that this alone is not sufficient when a more reliable silver mirror is sought.

The inventor of the present application has analyzed various prototypes from the viewpoint of the behavior of film stress with respect to environmental changes, and from the consideration of state changes in single-layer and multi-layer states, silver mirrors with extremely high reliability are the composition and film. In addition to the general layer structure such as thickness and film density, it was found that the change in film stress due to high temperature drying and high temperature humidity is small. That is, the inventor of the present application has determined a balance of the layer structure in which the change in film stress at high temperature drying and high temperature humidity is small, and by determining the quantitative value of the amount of change, a method for selecting a silver mirror with extremely high reliability can be obtained. I was able to establish it.

The silver reflector according to the present invention, its manufacturing method, and the inspection method have been described above in accordance with the embodiments or examples, but the silver reflector and the like according to the present invention are not limited to the above-mentioned specific examples. Absent.

For example, the film mainly composed of aluminum oxide constituting the adhesion layer 31 and the like can be formed not only by the above-mentioned ion assist method but also by another film forming method. Specifically, it can be formed by a sputtering method, an RF vapor deposition method, an ion plating method, a cluster ion beam (Ionized Cluster Beam) vapor deposition method, a plasma ion beam vapor deposition method, or the like.

Claims (15)

A silver reflecting mirror including a base adhesion layer, a main silver layer formed on the adhesion layer, and a hyperreflecting layer formed on the main silver layer as a reflection film.
The main silver layer is formed of either silver or an alloy mainly composed of silver.
The film stress after the film formation of the reflective film is in the range of +100 MPa to -100 MPa.
The film stress after the reflective film was put into a high temperature drying environment at 110 ° C. for 24 hours was in the range of +100 MPa to -100 MPa.
The film stress after the reflective film after being put into the high temperature and high temperature drying environment of 110 ° C. for 24 hours in the high temperature and high humidity environment of 85 ° C. and 85% RH is in the range of +100 MPa to -100 MPa, and
The absolute value of the amount of change between the film stress value after being put into the high temperature and dry environment of 110 ° C. for 24 hours and the film stress value after being put into the high temperature and high humidity environment of 85 ° C. and 85% RH for 24 hours is 40 MPa. The silver reflector below. The adhesion layer contains at least one layer mainly composed of aluminum oxide, and the layer mainly composed of aluminum oxide is formed by using an ion assist method, and is a film of the layer mainly composed of aluminum oxide. The silver reflector according to claim 1, wherein the stress is compressive stress. The adhesion layer and any one of the adhesion layer and the hyperreflection layer include at least two or more adjustment layers, and one adjustment layer is put into a high temperature drying environment at 110 ° C. for 24 hours in a single layer state. The film stress after being put into a high temperature and high humidity environment of 85 ° C. and 85% RH for 24 hours changes in the negative direction, and the other adjusting layer is dried at a high temperature of 110 ° C. in a single layer state. According to any one of claims 1 and 2, the film stress after being put into a hot and humid environment at 85 ° C. and 85% RH for 24 hours changes in the positive direction with respect to the film stress after being put into the environment for 24 hours. The silver reflector described. The silver reflector according to any one of claims 1 to 3 , wherein the additive material of the silver-based alloy is any one of Bi, Pd, Cu, Au, Ge, Nd, and Al. The adhesion layer includes at least two or more layers, and the material of each layer constituting the adhesion layer is selected from at least one of a material mainly composed of aluminum oxide, LaTIO ₃ , CeO ₂ , Y ₂ O ₃ and SnO _2. The silver reflector according to any one of claims 1 to 4 . The silver reflector according to claim 5 , wherein the material of the layer that directly adheres to the main silver layer among the adhesion layers is selected from at least one of LaTIO ₃ , CeO ₂ , Y ₂ O _3, and SnO ₂ . The brightening reflection layer includes at least three or more layers, and among the brightening reflection layers, the layer in direct contact with the main silver layer is formed of a material mainly made of aluminum oxide, claim 1 to 6 . The silver reflector according to any one item. The silver reflector according to any one of claims 1 to 7 , wherein the film stress of the reflective layer is negatively larger than −50 MPa. The silver reflector according to claim 2, wherein the refractive index of the layer mainly composed of aluminum oxide is 1.55 to 1.65. The hyperrefractive layer includes three or more layers, is formed of a material mainly composed of aluminum oxide, and alternately has a layer of a high refractive index material and a layer of a low refractive index material on a layer in close contact with the main silver layer. The high-refractive index material is selected from at least one of TiO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ , LaTIO ₃ , ZrO ₂ , and a mixed material of these materials. The silver reflector according to any one of claims 1 to 9 , wherein the low refractive index material is selected from at least one of SiO ₂ and a mixed material in which SiO ₂ is mixed with aluminum oxide. A method for inspecting a silver reflecting mirror, which includes an underlying adhesive layer, a main silver layer formed on the adhesive layer, and a hyperreflective layer formed on the main silver layer as a reflective film.
The main silver layer is formed of either silver or an alloy mainly composed of silver.
While determining whether or not the film stress after the film formation of the reflective film is in the range of +100 MPa to -100 MPa,
The film stress value after the reflective film was put into a high temperature drying environment of 110 ° C. for 24 hours, and the high temperature and humidity of 85 ° C. and 85% RH after the reflective film was put into a high temperature drying environment of 110 ° C. for 24 hours. A method for inspecting a silver reflector for determining whether or not the absolute value of the amount of change between the film stress value and the film stress value after being put into the environment for 24 hours is 40 MPa or less. It was determined whether or not the film stress after the reflective film was put into a high temperature drying environment at 110 ° C. for 24 hours was in the range of +100 MPa to -100 MPa.
It is determined whether or not the film stress after being put into the high temperature and high humidity environment of 85 ° C. and 85% RH for 24 hours after being put into the high temperature and dry environment of 110 ° C. is in the range of +100 MPa to -100 MPa. The method for inspecting a silver reflector according to claim 11 . When the adhesive layer contains a layer mainly composed of aluminum oxide formed by the ion assist method, it is determined whether or not the film stress of the layer mainly composed of aluminum oxide is a compressive stress. Item 12. The method for inspecting a silver reflector according to Item 12 . A method for manufacturing a silver reflecting mirror, which comprises a base adhesion layer, a main silver layer formed on the adhesion layer, and a hyperreflection layer formed on the main silver layer as a reflection film.
The main silver layer is formed of either silver or an alloy mainly composed of silver.
The film stress after the film formation of the reflective film is set in the range of +100 MPa to -100 MPa, and
The film stress value after the reflective film was put into a high temperature drying environment of 110 ° C. for 24 hours, and the high temperature and humidity of 85 ° C. and 85% RH after the reflective film was put into a high temperature drying environment of 110 ° C. for 24 hours. the absolute value of the change amount between the film stress value after turning 24 hours environment, manufacturing method of the silver reflecting mirror for below 40 MPa. The method for manufacturing a silver reflector according to claim 14 , wherein a test piece having the same structure as the silver reflector is produced and the film stress is measured.

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